Lymphocytic choriomeningitis virus (LCMV) is a single-stranded, ambisense RNA virus that is able to establish a noncytolytic, persistent infection in its natural host, the house mouse. This proposal is designed to delineate the mechanism(s) utilized by LCMV to regulate its replication during the establishment and maintenance of persistent infection. We will test, during persistent infection with LCMV, (a) whether the virus is able to become replicatively quiescent via maintenance of its genome in a strand-specific manner (genomic-sense), (b) whether the viral zinc binding (Z) protein is associated with this strand-specific maintenance of the genome, and (c) whether the accumulation of viral RNA segments containing small terminal deletions is associated with reduced viral protein expression and infectious virus production. To accomplish these aims, we will infect cell lines or Balb/c mice with LCMV, strain Armstrong, and collect cells or tissues at selected acute and persistent time points. From these samples, we will quantitate (a) the titers of each of the intact (genomic, antigenomic, or subgenomic) or terminally-deleted (genomic or antigenomic) viral RNA species produced during infection via real-time quantitative RT-PCR, (b) the titers of infectious virus via plaque assay, and (c) the levels of viral protein (Z, glycoprotein, or nucleoprotein) expression via Western blot and immunohistochemistry. The mechanisms by which RNA viruses (with the exception of retroviruses) establish and maintain persistent infection have yet to be fully understood. Through this proposal, we hope to provide novel insight into the mechanism(s) utilized by LCMV to establish and maintain persistent infection. Our findings could be applicable to other RNA viruses that cause persistent infection.